检查窗体是否打开
来自：NorthWind
作者：不祥
正文：
Function IsLoaded(ByVal strFormName As String) As Boolean
' 如果指定窗体在窗体视图或数据表视图中打开，返回 True。
Dim oAccessObject As AccessObject

Set oAccessObject = CurrentProject.AllForms(strFormName)
If oAccessObject.IsLoaded Then
If oAccessObject.CurrentView <> acCurViewDesign Then
IsLoaded = True
End If
End If
End Function